Embolization Device Constructed From Expansile Polymer

ABSTRACT

Devices for the occlusion of body cavities, such as the embolization of vascular aneurysms and the like, and methods for making and using such devices. The devices may be comprised of novel expansile materials, novel infrastructure design, or both. The devices provided are very flexible and enable deployment with reduced or no damage to bodily tissues, conduits, cavities, etceteras.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/254,962 filed Oct. 26, 2009 entitled Embolization DeviceConstructed From Expansile Polymer, which is hereby incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates to devices for the occlusion of bodycavities, such as the embolization of vascular aneurysms and the like,and methods for making and using such devices.

BACKGROUND OF THE INVENTION

The occlusion of body cavities, blood vessels, and other lumina byembolization is desired in a number of clinical situations. For example,the occlusion of fallopian tubes for the purposes of sterilization, andthe occlusive repair of cardiac defects, such as a patent foramen ovale,patent ductus arteriosis, and left atrial appendage, and atrial septaldefects. The function of an occlusion device in such situations is tosubstantially block or inhibit the flow of bodily fluids into or throughthe cavity, lumen, vessel, space, or defect for the therapeutic benefitof the patient.

The embolization of blood vessels is also desired in a number ofclinical situations. For example, vascular embolization has been used tocontrol vascular bleeding, to occlude the blood supply to tumors, and toocclude vascular aneurysms, particularly intracranial aneurysms. Inrecent years, vascular embolization for the treatment of aneurysms hasreceived much attention. Several different treatment modalities havebeen shown in the prior art. One approach that has shown promise is theuse of thrombogenic microcoils. These microcoils may be made ofbiocompatible metal alloy(s) (typically a radio-opaque material such asplatinum or tungsten) or a suitable polymer. Examples of microcoils aredisclosed in the following patents: U.S. Pat. No. 4,994,069—Ritchart etal.; U.S. Pat. No. 5,133,731—Butler et al.; U.S. Pat. No. 5,226,911—Cheeet al.; U.S. Pat. No. 5,312,415—Palermo; U.S. Pat. No. 5,382,259—Phelpset al.; U.S. Pat. No. 5,382,260—Dormandy, Jr. et al.; U.S. Pat. No.5,476,472—Dormandy, Jr. et al.; U.S. Pat. No. 5,578,074—Mirigian; U.S.Pat. No. 5,582,619—Ken; U.S. Pat. No. 5,624,461—Mariant; U.S. Pat. No.5,645,558—Horton; U.S. Pat. No. 5,658,308—Snyder; and U.S. Pat. No.5,718,711—Berenstein et al; all of which are hereby incorporated byreference.

A specific type of microcoil that has achieved a measure of success isthe Guglielmi Detachable Coil (“GDC”), described in U.S. Pat. No.5,122,136—Guglielmi et al. The GDC employs a platinum wire coil fixed toa stainless steel delivery wire by a solder connection. After the coilis placed inside an aneurysm, an electrical current is applied to thedelivery wire, which electrolytically disintegrates the solder junction,thereby detaching the coil from the delivery wire. The application ofcurrent also creates a positive electrical charge on the coil, whichattracts negatively-charged blood cells, platelets, and fibrinogen,thereby increasing the thrombogenicity of the coil. Several coils ofdifferent diameters and lengths can be packed into an aneurysm until theaneurysm is completely filled. The coils thus create and hold a thrombuswithin the aneurysm, inhibiting its displacement and its fragmentation.

A more recent development in the field of microcoil vaso-occlusivedevices is exemplified in U.S. Pat. No. 6,299,619 to Greene, Jr. et al.,U.S. Pat. No. 6,602,261 to Greene, Jr. et al., and co-pending U.S.patent application Ser. No. 10/631,981 to Martinez; all assigned to theassignee of the subject invention and incorporated herein by reference.These patents disclose vaso-occlusive devices comprising a microcoilwith one or more expansile elements disposed on the outer surface of thecoil. The expansile elements may be formed of any of a number ofexpansile polymeric hydrogels, or alternatively,environmentally-sensitive polymers that expand in response to a changein an environmental parameter (e.g., temperature or pH) when exposed toa physiological environment, such as the blood stream.

This invention is a novel vaso-occlusive device, a novel expansileelement, and a combination thereof.

SUMMARY OF THE INVENTION

The present invention is directed to novel vaso-occlusive devicescomprising a carrier member, one or more novel expansile elements, and acombination thereof. Generally, the expansile element or elementscomprise an expansile polymer. The carrier member may be used to assistthe delivery of the expansile element by providing a structure that, insome embodiments, allows coupling to a delivery mechanism and, in someembodiments, enhances the radiopacity of the device.

In one embodiment, the expansile polymer is an environmentally sensitivepolymeric hydrogel, such as that described in U.S. Pat. No. 6,878,384,issued Apr. 12, 2005 to Cruise et al., hereby incorporated by reference.In another embodiment, the expansile polymer is a novel hydrogelcomprised of sodium acrylate and a poly(ethylene glycol) derivative. Inanother embodiment, the expansile polymer is a hydrogel comprising aPluronics® derivative.

In one embodiment, the expansile polymer is a novel hydrogel that hasionizable functional groups and is made from macromers. The macromersmay be non-ionic and/or ethylenically unsaturated.

In one embodiment, the macromers may have a molecular weight of about400 to about 35,000 grams/mole. In another embodiment the macromers mayhave a molecular weight of about 5,000 to about 15,000 grams/mole. Inyet another embodiment the macromers may have a molecular weight ofabout 7,500 to about 12,000 grams/mole. In one embodiment the macromershave a molecular weight of 8,000 grams/mole.

In one embodiment, the hydrogel may be made of polyethers,polyurethanes, derivatives thereof, or combinations thereof. In anotherembodiment, the ionizable functional groups may comprise basic groups(e.g., amines, derivatives thereof, or combinations thereof) or acidicgroups (e.g., carboxylic acids, derivatives thereof, or combinationsthereof). If the ionizable functional groups comprise basic groups, thebasic groups may be deprotonated at pHs greater than the pKa orprotonated at pHs less than the pKa of the basic groups. If theionizable functional groups comprise acidic groups, the acidic groupsmay be protonated at pHs less than the pKa or de-protonated at pHsgreater than the pKa of the acidic groups.

In one embodiment, the macromers may comprise vinyl, acrylate,acrylamide, or methacrylate derivatives of poly(ethylene glycol), orcombinations thereof. In another embodiment, the macromer may comprisepoly(ethylene glycol) di-acrylamide. In another embodiment, the hydrogelis substantially free, more preferably free of unbound acrylamide.

In one embodiment, the macromers may be cross-linked with a compoundthat contains at least two ethylenically unsaturated moities. Examplesof ethylenically unsaturated compounds include N,N′-methylenebisacrylamide, derivatives thereof, or combinations thereof.In another embodiment, the hydrogel may be prepared using apolymerization initiator. Examples of suitable polymerization initiatorscomprise N,N,N′,N′-tetramethylethylenediamine, ammonium persulfate,azobisisobutyronitrile, benzoyl peroxides, derivatives thereof, orcombinations thereof. The polymerization initiator may be soluble inaqueous or organic solvents. For example, azobisisobutyronitrile is notwater soluble; however, water soluble derivatives ofazobisisobutyronitrile, such as 2,2′-azobis(2-methylproprionamidine)dihydrochloride, are available. In another embodiment, the hydrogel maybe substantially non-resorbable, non-degradable or both, atphysiological conditions.

In one embodiment, the invention comprises a method for preparing anenvironmentally-responsive hydrogel for implantation in an animal. Themethod includes combining at least one, preferably non-ionic, macromerwith at least one ethylenically unsaturated moiety, at least onemacromer or monomer having at least one ionizable functional group andat least one ethylenically unsaturated moiety, at least onepolymerization initiator, and at least one solvent to form a hydrogel.The solvent may include aqueous or organic solvents, or combinationsthereof. In another embodiment, the solvent is water. Next, the hydrogelmay be treated to prepare an environmentally-responsive hydrogel,preferably one that is responsive at physiological conditions. Theionizable functional group(s) may be an acidic group (e.g., a carboxylicacid, a derivative thereof, or combinations thereof) or a basic group(e.g., an amine, derivatives thereof, or combinations thereof). If theionizable functional group comprises an acidic group, the treating stepmay comprise incubating the hydrogel in an acidic environment toprotonate the acidic groups. If the ionizable functional group comprisesa basic group, the treating step may comprise incubating the hydrogel ina basic environment to de-protonate the basic groups. In certainembodiments, it is preferable that the acidic groups are capable ofbeing de-protonated or, conversely, the basic groups are capable ofbeing protonated, after implantation in an animal.

In one embodiment, the ethylenically unsaturated macromer may have avinyl, acrylate, methacrylate, or acrylamide group; includingderivatives thereof or combinations thereof. In another embodiment, theethylenically unsaturated macromer is based upon poly(ethylene glycol),derivatives thereof, or combinations thereof. In another embodiment, theethylenically unsaturated macromer is poly(ethylene glycol)di-acrylamide, poly(ethylene glycol) di-acrylate, poly(ethylene glycol)di-methacrylate, derivatives thereof, or combinations thereof. Inanother embodiment, the ethylenically unsaturated macromer ispoly(ethylene glycol) di-acrylamide. The ethylenically unsaturatedmacromer may be used at a concentration of about 5% to about 40% byweight, more preferably about 20% to about 30% by weight. The solventmay be used at a concentration of about 20% to about 80% by weight.

In one embodiment, the combining step also includes adding at least onecross-linking agent comprising an ethylenically unsaturated compound. Incertain embodiments of the present invention, a cross-linker may not benecessary. In other words, the hydrogel may be prepared using a macromerwith a plurality of ethylenically unsaturated moieties. In anotherembodiment, the polymerization initiator may be a reduction-oxidationpolymerization initiator. In another embodiment, the polymerizationinitiator may be N,N,N′,N′-tetramethylethylenediamine, ammoniumpersulfate, azobisisobutyronitrile, benzoyl peroxides,2,2′-azobis(2-methylproprionamidine) dihydrochloride, derivativesthereof, or combinations thereof. In another embodiment, the combiningstep further includes adding a porosigen.

In one embodiment, the ethylenically unsaturated macromer includespoly(ethylene glycol) di-acrylamide, the macromer or monomer or polymerwith at least one ionizable group and at least one ethylenicallyunsaturated group includes sodium acrylate, the polymerization initiatorincludes ammonium persulfate and N,N,N,′,N′ tetramethylethylenediamine,and the solvent includes water.

In one embodiment, the ethylenically unsaturated macromer has amolecular weight of about 400 to about 35,000 grams/mole. In anotherembodiment, the ethylenically unsaturated macromer has a molecularweight of about 5,000 to about 15,000 grams/mole. In one embodiment, theethylenically unsaturated macromer has a molecular weight of about 7,500to about 12,000 grams/mole. In another embodiment, theenvironmentally-responsive hydrogel is substantially non-resorbable, ornon-degradable or both at physiological conditions. In certainembodiments, the environmentally-responsive hydrogel may besubstantially free or completely free of unbound acrylamide.

In one embodiment, the carrier member comprises a coil or microcoil madefrom metal, plastic, or similar materials. In another embodiment, thecarrier member comprises a braid or knit made from metal, plastic, orsimilar materials. In another embodiment, the carrier member comprises aplastic or metal tube with multiple cuts or grooves cut into the tube.

In one embodiment, the expansile element is arranged generallyco-axially within the carrier member. In another embodiment, a stretchresistant member is arranged parallel to the expansile element. Inanother embodiment, the stretch resistant member is wrapped, tied, ortwisted around the expansile element. In another embodiment, the stretchresistant member is positioned within the expansile element. In anotherembodiment, the stretch resistant member is located within or partiallysurrounded by the expansile element.

In one embodiment, the device comprising the expansile element andcarrier member are detachably coupled to a delivery system. In anotherembodiment, the device is configured for delivery by pushing orinjecting through a conduit into a body.

In one embodiment, the expansile element is environmentally sensitiveand exhibits delayed expansion when exposed to bodily fluids. In anotherembodiment, the expansile element expands quickly upon contact with abodily fluid. In another embodiment, the expansile element comprises aporous or reticulated structure that may form a surface or scaffold forcellular growth.

In one embodiment, the expansile element expands to a dimension that islarger than the diameter of the carrier member in order to provideenhanced filling of the lesion. In another embodiment, the expansileelement expands to a dimension equal to or smaller than the diameter ofthe carrier member to provide a scaffold for cellular growth, release oftherapeutic agents such as pharmaceuticals, proteins, genes, biologiccompounds such as fibrin, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing one embodiment of the presentinvention prior to expansion of the expansile element;

FIG. 2 is a perspective view showing a device similar to FIG. 1 in anexpanded state;

FIG. 3 is a perspective view of an alternative embodiment of the presentinvention;

FIG. 4 is a perspective view of an alternative embodiment wherein thecarrier member comprises a fenestrated tube, braid or knit;

FIG. 5 is a perspective view of an alternative embodiment incorporatinga stretch resistant member running approximately parallel to theexpansile element;

FIG. 6 is a perspective view of an alternative embodiment incorporatinga stretch resistant member approximately intertwined with the expansileelement;

FIG. 7 is a perspective view of an alternative embodiment wherein theexpansile element has formed a loop or fold outside the carrier member.

FIG. 8 is a perspective view of an alternative embodiment showing adevice similar to those shown in FIG. 1 and FIG. 2 wherein the expansileelement is not expanded to a diameter larger than the carrier member.

FIG. 9 is a side view of an embodiment showing a device similar to thoseshown in FIG. 1 and FIG. 2.

FIG. 10 is an exploded perspective view of the device of FIG. 9.

FIG. 11 is a side view of the device of FIG. 9 connected to a deliverydevice.

FIG. 12 is a side view of a preferred embodiment of an implant accordingto the present invention.

FIG. 13 is a said view of a preferred embodiment of an implant accordingto the present invention.

DESCRIPTION OF THE INVENTION

As used herein, the term “macromer” refers to a large moleculecontaining at least one active polymerization site or binding site.Macromers have a larger molecular weight than monomers. For example, anacrylamide monomer has a molecular weight of about 71.08 grams/molewhereas a poly(ethylene glycol) di-acrylamide macromer may have amolecular weight of about 400 grams/mole or greater. Preferred macromersare non-ionic, i.e. they are uncharged at all pHs.

As used herein, the term “environmentally responsive” refers to amaterial (e.g., a hydrogel) that is sensitive to changes in environmentincluding but not limited to pH, temperature, and pressure. Many of theexpansile materials suitable for use in the present invention areenvironmentally responsive at physiological conditions.

As used herein, the term “non-resorbable” refers to a material (e.g., ahydrogel) that cannot be readily and/or substantially degraded and/orabsorbed by bodily tissues.

As used herein, the term “unexpanded” refers to the state at which ahydrogel is substantially not hydrated and, therefore, not expanded.

As used herein, the term “ethylenically unsaturated” refers to achemical entity (e.g., a macromer, monomer or polymer) containing atleast one carbon-carbon double bond.

Referring to FIG. 1-8, the device comprises an expansile element 1 and acarrier member 2. The expansile element 1 may be made from a variety ofsuitable biocompatible polymers. In one embodiment, the expansileelement 1 is made of a bioabsorbable or biodegradable polymer, such asthose described in U.S. Pat. Nos. 7,070,607 and 6,684,884, thedisclosures of which are incorporated herein by reference. In anotherembodiment, the expansile element 1 is made of a soft conformalmaterial, and more preferably of an expansile material such as ahydrogel.

In one embodiment, the material forming the expansile element 1 is anenvironmentally responsive hydrogel, such as that described in U.S. Pat.No. 6,878,384, the disclosure of which is incorporated herein byreference. Specifically, the hydrogels described in U.S. Pat. No.6,878,384 are of a type that undergoes controlled volumetric expansionin response to changes in such environmental parameters as pH ortemperature. These hydrogels are prepared by forming a liquid mixturethat contains (a) at least one monomer and/or polymer, at least aportion of which is sensitive to changes in an environmental parameter;(b) a cross-linking agent; and (c) a polymerization initiator. Ifdesired, a porosigen (e.g., NaCl, ice crystals, or sucrose) may be addedto the mixture, and then removed from the resultant solid hydrogel toprovide a hydrogel with sufficient porosity to permit cellular ingrowth.The controlled rate of expansion is provided through the incorporationof ethylenically unsaturated monomers with ionizable functional groups(e.g., amines, carboxylic acids). For example, if acrylic acid isincorporated into the cross-linked network, the hydrogel is incubated ina low pH solution to protonate the carboxylic acid groups. After theexcess low pH solution is rinsed away and the hydrogel dried, thehydrogel can be introduced through a microcatheter filled with saline atphysiological pH or with blood. The hydrogel cannot expand until thecarboxylic acid groups deprotonate. Conversely, if an amine-containingmonomer is incorporated into the cross-linked network, the hydrogel isincubated in a high pH solution to deprotonate amines. After the excesshigh pH solution is rinsed away and the hydrogel dried, the hydrogel canbe introduced through a microcatheter filled with saline atphysiological pH or with blood. The hydrogel cannot expand until theamine groups protonate.

In another embodiment, the material forming the expansile element 1 maybe an environmentally responsive hydrogel, similar to those described inU.S. Pat. No. 6,878,384; however, an ethylenically unsaturated, andpreferably non-ionic, macromer replaces or augments at least one monomeror polymer. The Applicants surprisingly have discovered that hydrogelsprepared in accordance with this embodiment can be softer and/or moreflexible in their unexpanded state than those prepared in accordancewith U.S. Pat. No. 6,878,384. The Applicants also have discovered thatethylenically unsaturated and non-ionic macromers (e.g., poly(ethyleneglycol) and derivatives thereof) may be used not only to prepare asofter unexpanded hydrogel; but, in combination with monomers orpolymers containing ionizable groups, one that also may be treated to bemade environmentally responsive. The surprising increase in unexpandedflexibility enables the hydrogels to be, for example, more easilydeployed in an animal or deployed with reduced or no damage to bodilytissues, conduits, cavities, etceteras.

The hydrogels prepared from non-ionic macromers in combination withmonomers or polymers with ionizable functional groups still are capableof undergoing controlled volumetric expansion in response to changes inenvironmental parameters. These hydrogels may be prepared by combiningin the presence of a solvent: (a) at least one, preferably non-ionic,macromer with a plurality of ethylenically unsaturated moieties; (b) amacromer or polymer or monomer having at least one ionizable functionalgroup and at least one ethylenically unsaturated moiety; and (c) apolymerization initiator. It is worthwhile to note that with this typeof hydrogel, a cross-linking agent may not be necessary forcross-linking since, in certain embodiments, the components selected maybe sufficient to form the hydrogel. As hereinbefore described, aporosigen may be added to the mixture and then removed from theresultant hydrogel to provide a hydrogel with sufficient porosity topermit cellular ingrowth.

The non-ionic macromer-containing hydrogels' controlled rate ofexpansion may be provided through the incorporation of at least onemacromer or polymer or monomer having at least one ionizable functionalgroup (e.g., amine, carboxylic acid). As discussed above, if thefunctional group is an acid, the hydrogel is incubated in a low pHsolution to protonate the group. After the excess low pH solution isrinsed away and the hydrogel dried, the hydrogel can be introducedthrough a microcatheter, preferably filled with saline. The hydrogelcannot expand until the acid group(s) deprotonates. Conversely, if thefunctional group is an amine, the hydrogel is incubated in a high pHsolution to deprotonate the group. After the excess high pH solution isrinsed away and the hydrogel dried, the hydrogel can be introducedthrough a microcatheter, preferably filled with saline. The hydrogelcannot expand until the amine(s) protonates.

More specifically, in one embodiment, the hydrogel is prepared bycombining at least one non-ionic macromer having at least oneunsaturated moiety, at least one macromer or monomer or polymer havingat least one ionizable functional group and at least one ethylenicallyunsaturated moiety, at least one polymerization initiator, and asolvent. Optionally, an ethylenically unsaturated cross-linking agentand/or a porosigen also may be incorporated. In one embodiment,concentrations of the non-ionic macromers in the solvent range fromabout 5% to about 60% (w/w). In another embodiment, concentrations ofthe non-ionic macromers in the solvent range from about 20% to about 30%(w/w). In one embodiment, concentrations of the non-ionic macromers inthe solvent range are about 25% (w/w). In one embodiment the non-ionicmacromer is poly(ethylene glycol), its derivatives, and combinationsthereof. Derivatives include, but are not limited to, poly(ethyleneglycol) di-acrylamide, poly(ethylene glycol) di-acrylate, andpoly(ethylene glycol) dimethacrylate. Poly(ethylene glycol)di-acrylamide is a preferred derivative of poly(ethylene glycol) and hasa molecular weight ranging from about 8,500 grams/mole to about 12,000grams/mole. The macromer may have less than 20 polymerization sites,more preferably less than 10 polymerization sites, more preferably aboutfive or less polymerization sites, and more preferably from about two toabout four polymerization sites. Poly(ethylene glycol) di-acrylamide hastwo polymerization sites.

Preferred macromers or polymers or monomers having at least oneionizable functional group include, but are not limited to compoundshaving carboxylic acid or amino moieties or, derivatives thereof, orcombinations thereof. Sodium acrylate is a preferred ionizablefunctional group-containing compound and has a molecular weight of 94.04g/mole. In one embodiment, concentrations of the ionizable macromers orpolymers or monomers in the solvent range from about 5% to about 60%(w/w) In another embodiment, concentrations of the ionizable macromersor polymers or monomers in the solvent range from about 20% to about 30%(w/w). In one embodiment, concentrations of the ionizable macromers orpolymers or monomers in the solvent are about 27% (w/w). In someembodiments, at least about 10%-50% of the ionizable macromers orpolymers or monomers selected should be pH sensitive. In otherembodiments at least about 10%-30% of the ionizable macromers orpolymers or monomers selected should be pH sensitive. In one embodimentno free acrylamide is used in the macromer-containing hydrogels of thepresent invention.

When used, the cross-linking agent may be any multifunctionalethylenically unsaturated compound, preferably N,N′-methylenebisacrylamide. If biodegradation of the hydrogel material isdesired, a biodegradable cross-linking agent may be selected. Theconcentrations of the cross-linking agent in the solvent should be lessthan about 1% w/w, and preferably less than about 0.1% (w/w).

As described above, if a solvent is added, it may be selected based onthe solubilities of the macromer(s) or monomer(s) or polymer(s),cross-linking agent, and/or porosigen used. If a liquid macromer ormonomer or polymer solution is used, a solvent may not be necessary. Apreferred solvent is water, but a variety of aqueous and organicsolvents may be used. In one embodiment, concentrations of the solventrange from about 20% to about 80% (w/w). In another embodiment,concentrations of the solvent range from about 40% to about 60% (w/).

Crosslink density may be manipulated through changes in the macromer ormonomer or polymer concentration, macromer molecular weight, solventconcentration and, when used, cross-linking agent concentration. Asdescribed above, the hydrogel may be cross-linked viareduction-oxidation, radiation, and/or heat. A preferred type ofpolymerization initiator is one that acts via reduction-oxidation.Suitable polymerization initiators include, but are not limited to,N,N,N′,N′-tetramethylethylenediamine, ammonium persulfate,azobisisobutyronitrile, benzoyl peroxides,2,2′-azobis(2-methylpropionamidine) dihydrochloride, derivativesthereof, or combinations thereof. A combination of ammonium persulfateand N,N,N′,N′-tetramethylethylenediamine is a preferred polymerizationinitiator for use in the macromer containing embodiments of theinvention.

After polymerization is complete, the hydrogels of the present inventionmay be washed with water, alcohol or other suitable washing solution(s)to remove any porosigen(s), any unreacted, residual macromer(s),monomer(s), and polymer(s) and any unincorporated oligomers. Preferablythis is accomplished by initially washing the hydrogel in distilledwater.

Porosity may be imparted into the solid hydrogel through the use ofporosigens such as sodium chloride, ice crystals, or sucrose.Polymerization of the monomer solution around the solid particles insuspension and subsequent removal of the solid particles from thehydrogel can provide a hydrogel with sufficient porosity to permitcellular ingrowth. A preferred porosigen is sodium chloride withparticles less than 10 microns in diameter. Preferred sodium chlorideconcentrations in the monomer solution range from 0.2 to 0.4 g sodiumchloride per g monomer solution.

The hydrogels of the present invention may be madeenvironmentally-responsive by protonating or deprotonating the ionizablefunctional groups present on the hydrogel network, as discussed above.Once the hydrogel has been prepared and, if needed, washed, the hydrogelmay be treated to make the hydrogel environmentally-responsive. Forhydrogel networks where the ionizable functional groups are carboxylicacid groups, the hydrogel is incubated in a low pH solution. The freeprotons in the solution protonate the carboxylic acid groups on thehydrogel network. The duration and temperature of the incubation and thepH of the solution influence the amount of control on the expansionrate. In general, the duration and temperature of the incubation aredirectly proportional to the amount of expansion control, while theincubation solution pH is inversely proportional thereto.

It has been determined that incubation solution water content alsoaffects expansion control. In this regard, higher water content enablesgreater hydrogel expansion and is thought to increase the number ofprotonation-accessible carboxylic acid groups. An optimization of watercontent and pH is required for maximum control on expansion rate.Expansion control, among other things, has an effect on devicepositioning/repositioning time. Typically, a positioning/repositioningtime of about 0.1 to about 30 minutes is preferred for hydrogel devicesin accordance with the present invention.

After incubation, the excess treating solution is washed away and thehydrogel material is dried. A hydrogel treated with the low pH solutionhas been observed to dry down to a smaller dimension than an untreatedhydrogel. This effect is desirable since devices containing thesehydrogels may be delivered through a microcatheter.

For hydrogel networks where the ionizable functional groups are aminegroups, the hydrogel is incubated in a high pH solution. Unlikecarboxylic acid functional groups, deprotonation occurs on the aminegroups of the hydrogel network at high pH. Aside from incubationsolution pH, the incubation is carried out similarly to that of thecarboxylic acid containing hydrogels. In other words, the duration andtemperature of the incubation and the pH of the solution are directlyproportional to the amount of expansion control. After incubation isconcluded, the excess treating solution is washed away and the hydrogelmaterial is dried.

In a preferred embodiment, the expansile element 1 is an expansilehydrogel comprised of (a) at least one, preferably non-ionic,ethylenically unsaturated macromer or monomer or polymer having at leasttwo cross-linkable groups; (b) at least one monomer and/or polymer whichhas at least one cross-linkable groups, and at least one moiety that issensitive to changes in an environmental parameter; and (c) apolymerization initiator. In some embodiments, the monomers and polymersmay be water soluble, while in other embodiments they may be non-watersoluble. Suitable polymers for component (a) include poly(ethyleneglycol), poly(ethylyene oxide), poly(vinyl alcohol), poly(propyleneoxide), poly(propylene glycol), poly(ethylene oxide)-co-poly(propyleneoxide), poly(vinyl pyrrolidinone), poly(amino acids), dextrans,poly(ethyloxazoline), polysaccharides, proteins, glycosaminoglycans, andcarbohydrates, and derivatives thereof. The preferred polymer ispoly(ethylene glycol) (PEG), especially for component (a).Alternatively, polymers that biodegrade partly or completely may beutilized.

One embodiment comprises combining in the presence of a solvent (a)about 5% to about 50% of a non-ionic, ethylenically unsaturated macromeror monomer or polymer; (b) about 5% to about 60% of an ethylenicallyunsaturated monomer or polymer with at least one ionizable functionalgroup; and, (c) a polymerization initiator. Suitable ionizable,ethylenically unsaturated monomers include acrylic acid and methacrylicacid, as well as derivatives thereof. One suitable monomer having atleast one ionizable functional group is sodium acrylate. Suitablemacromers with two ethylenically unsaturated moities includepoly(ethylene glycol) di-acrylate and poly(ethylene glycol)di-acrylamide, and poly(ethylene glycol) di-acrylamide, which havemolecular weights ranging between 400 and 30,000 grams/mole. The use ofmacromers with a plurality of ethylenically unsaturated groups permitsthe elimination of the cross-linker, as the cross-linker functions areperformed by the multi-functional polymer. In one embodiment, thehydrogel comprises, about 5% to about 60% sodium acrylate, about 5% toabout 50% poly(ethylene glycol) di-acrylamide.

A sodium acrylate/poly(ethylene glycol) di-acrylamide hydrogel is usedto enhance the mechanical properties of the previously-describedenvironmentally responsive hydrogel. Since a sodiumacrylate/poly(ethylene glycol) di-acrylamide hydrogel is softer than asodium acrylate/acrylamide hydrogel (e.g., the one utilized in HydrogelEmbolic System (HES) made by MicroVention, Aliso Viejo, Calif.), devicesincorporating it may be more flexible. Due to the relative stiffness ofthe HES, MicroVention recommends pre-softening the device by soaking inwarm fluid or steaming the implant. In addition, devices made fromacrylamide are relatively straight before pre-softening because thestiffness of the acrylamide-based hydrogel prevents the carrier member(for the HES, a microcoil) from assuming its secondary configuration.Devices made from a sodium acrylate/poly(ethylene glycol) di-acrylamidehydrogel may not require pre-softening techniques such as soaking inwarm fluid such as saline or blood or exposure to steam in order to forminto a secondary configuration heat-set into the carrier member 2 or asimilar carrier member. Thus, in embodiments comprising, for example,sodium acrylate and poly(ethylene glycol) di-acrylamide, a substantiallycontinuous length of hydrogel disposed either within the lumen 3 of thecarrier member 2 as shown in, for example, FIG. 1 or on a carrierelement such as those shown in the Martinez '981 application or Greene'261, will form into the secondary configuration pre-formed into thecarrier member without pre-treatment (e.g. exposure to steam, fluid, orblood). This makes the device easier to use because it allowselimination of the pre-treatment step and the device may be safer whendeployed into the patient because a softer device is less likely tocause damage to the lesion.

Examples

3 g of acrylamide, 1.7 g of acrylic acid, 9 mg of bisacrylamide, 50 mgof N,N,N′,N′-tetramethylethylenediamine, 15 mg of ammonium persulfate,and 15.9 g water were combined and polymerized in a 0.020 inch tube. Thetubularized polymer was removed from the tubing to prepare Hydrogel 1 inaccordance with U.S. Pat. No. 6,878,384.

4.6 g of poly(ethylene glycol) diacrylamide, 3.3 g of sodium acrylate,100 mg of N,N,N′,N′-tetramethylethylenediamine, 25 mg of ammoniumpersulfate, and 15.9 g water were combined and polymerized in a 0.020inch tube. The tubularized polymer was removed from the tubing toprepare Hydrogel 2, in accordance with a macromer-containing hydrogelembodiment of the present invention.

A large platinum microcoil for the above examples has a 0.014 inch outerdiameter and a 0.0025 inch filar. A small platinum microcoil has a 0.010inch outer diameter and a 0.002 inch filar.

8.3 g of poly(ethylene glycol) diacrylamide, 9.0 g of sodium acrylate,155 mg of N,N,N′,N′-tetramethylethylenediamine, 20 mg of ammoniumpersulfate, and 15.9 g water were combined and polymerized in a 0.025inch tube. The tubularized polymer was removed from the tubing toprepare Hydrogel 3, in accordance with a macromer-containing hydrogelembodiment of the present invention.

The Hydrogel 3 is distinct from the Hydrogel 1 and 2 examples. TheHydrogel 3 has a reduced stiffness relative to Hydrogel 1 and it furtherdoes not require pretreatment prior to use. Such pretreatment cansometimes require soaking in warm fluid or steaming to achieve a desiredflexibility. Hydrogel 3 also allows for increased expansion comparedwith Hydrogel 2.

In another embodiment, monomers are used to impart moieties to theexpansile element 1 that are suitable for coupling bioactive compounds,for example anti-inflammatory agents such as corticosteroids (e.g.prednisone and dexamethasone); or vasodilators such as nitrous oxide orhydralazine; or anti-thrombotic agents such as aspirin and heparin; orother therapeutic compounds, proteins such as mussel adhesive proteins(MAPs), amino acids such as 3-(3,4-dihydroxyphenyl)-L-alanine (DOPA),genes, or cellular material; see U.S. Pat. No. 5,658,308, WO 99/65401,Polymer Preprints 2001, 42(2), 147 Synthesis and Characterization ofSelf-Assembling Block Copolymers Containing Adhesive Moieties by KuiHwang et. al., and WO 00/27445; the disclosures of which are herebyincorporated by reference. Examples of moieties for incorporation intohydrogel materials include, but are not limited to, hydroxyl groups,amines, and carboxylic acids.

In another embodiment, the expansile element 1 may be renderedradiopaque by incorporation of monomers and/or polymers containing, forexample, iodine, or the incorporation of radiopaque metals such astantalum and platinum.

In some embodiments, the carrier member 2 is a flexible, elongatestructure. Suitable configurations for the carrier member 2 includehelical coils, braids, and slotted or spiral-cut tubes. The carriermember 2 may be made of any suitable biocompatible metal or polymer suchas platinum, tungsten, PET, PEEK, Teflon, Nitinol, Nylon, steel, and thelike. The carrier member may be formed into a secondary configurationsuch as helix, box, sphere, flat rings, J-shape, S-shape or othercomplex shape known in the art. Examples of appropriate shapes aredisclosed in Horton 5,766,219; Schaefer application Ser. No. 10/043,947;and Wallace 6,860,893; all hereby incorporated by reference.

As previously described, some embodiments of the instant invention maycomprise polymers that are sufficiently soft and flexible that asubstantially continuous length of the expansile element 1 will forminto a secondary configuration similar to the configuration originallyset into the carrier member 2 without pre-softening the device orexposing it to blood, fluid, or steam.

In some embodiments, the carrier member 2 incorporates at least one gap7 that is dimensioned to allow the expansile element 1 to expand throughthe gap (one embodiment of this configuration is shown in FIGS. 1-2). Inother embodiments, the carrier member 2 incorporates at least one gap 7that allows the expansile element 1 to be exposed to bodily fluids, butthe expansile element 1 does not necessarily expand through the gap (oneembodiment of this configuration is shown in FIG. 8). In otherembodiments, no substantial gap is incorporated into the carrier member2. Rather, fluid is allowed to infiltrate through the ends of the deviceor is injected through a lumen within the delivery system and theexpansile element 1 expands and forces its way through the carriermember 2.

In one embodiment shown in FIG. 1, the expansile element 1 comprises anacrylamide or poly(ethylene glycol)-based expansile hydrogel. Thecarrier member 2 comprises a coil. At least one gap 7 is formed in thecarrier member 2. The expansile element 1 is disposed within the lumen 3defined by the carrier member 2 in a generally coaxial configuration. Atip 4 is formed at the distal end of the device 11 by, for example, alaser, solder, adhesive, or melting the hydrogel material itself. Theexpansile element 1 may run continuously from the proximal end to thedistal end, or it may run for a portion of the device then terminatebefore reaching the distal or proximal end, or both.

As an example, in one embodiment the device is dimensioned to treat acerebral aneurysm. Those skilled in the art will appreciate that thedimensions used in this example could be re-scaled to treat larger orsmaller lesions. In this embodiment, the expansile element 1 is about0.006″-0.007″ before expansion and about 0.02″ after expansion. Theexpansile element is, for example, approximately 52% sodium acrylate,48% poly(ethylene glycol) di-acrylamide with a molecular weight about8000 grams/mole. About 0.4 g/g sodium chloride (about 10 micron particlesize) is used as a porosigen and about 0.6 mg/mL ammonium persulfate and7 mg/mL tetramethylethylene diamine is used as an initiator. The carriermember 2 in this embodiment is a microcoil in the range of about0.012″-0.0125″ in diameter and has a filar between about0.002″-0.00225″. In one embodiment, the carrier member 2 comprises atleast one gap 7 between 1 to 3 filar sizes long. In another embodiment,the carrier member 2 comprises at least one gap 7 that is about 2 filarslong. In one embodiment the size of the gap 7 is between about 0.0015inches and 0.0075 inches long. In another embodiment, the size of thegap 7 is between 0.00225 inches and 0.00750 inches long.

A coupler 13 is placed near the proximal end to allow the implant 11 tobe detachably coupled to a delivery system or pushed or injected througha catheter. Examples of delivery systems are found in co-pendingapplication Ser. No. 11/212,830 to Fitz, U.S. Pat. No. 6,425,893 toGuglielmi, U.S. Pat. No. 4,994,069 to Ritchart, U.S. Pat. No. 6,063,100to Diaz, and U.S. Pat. No. 5,690,666 to Berenstein; the disclosures ofwhich are hereby incorporated by reference.

In this embodiment, the implant 11 is constructed by formulating andmixing the hydrogel material as previously described in order to formthe expansile element 1. The carrier member 2 is wound around a helicalor complex form, and then heat-set by techniques known in the art toform a secondary diameter ranging from 0.5 mm to 30 mm and a lengthranging from 5 mm to 100 cm. After processing, washing, and optionalacid treatment, the expansile element 1 is threaded through the lumen 3of the carrier member 2. The distal end of the expansile element 1 isthen tied, for example by forming a knot, to the distal end of thecarrier member 2. Adhesive, such as UV curable adhesive or epoxy, may beused to further enhance the bond between the expansile element 1 and thecarrier member 2 and to form the distal tip 4. Alternatively, the tipmay be formed by, for example, a laser weld or solder ball.

In some embodiments, the size of the gap 7 and the ratio of expansion,loops or folds 12 may form as shown in FIG. 7 as the expansile element 1expands. It is desirable to prevent these loops or folds 12 fromforming. This can be done by stretching the expansile element 1 eitherbefore placing it within the carrier member 2 or after the distal end ofthe expansile element 1 is secured to the carrier member 2. For example,once the distal end of the expansile element 1 is secured to the carriermember 2, the expansile element 1 is stretched such that its initialdiameter of 0.010″ is reduced to between about 0.006:-0.007″ beforeplacing it within the carrier member 2. After stretching, the expansileelement 1 may be trimmed to match the length of the carrier member 2 andthen bonded near the proximal end of the carrier member 2 by, forexample, tying a knot, adhesive bonding, or other techniques known inthe art.

Once the implant 11 has been constructed, it is attached to a deliverysystem previously described by methods known in the art. The device mayalso be exposed to, for example, e-beam or gamma radiation to cross-linkthe expansile element 1 and to control its expansion. This is describedin U.S. Pat. No. 6,537,569 which is assigned to the assignee of thisapplication and hereby incorporated by reference.

Previously, the secondary dimensions of prior devices (e.g. HES) aregenerally sized to a dimension 1-2 mm smaller than the dimension (i.e.volume) of the treatment site due to the relative stiffness of thesedevices. The increased flexibility and overall design of the implant 11of the instant invention allows the secondary shape of the implant 11 tobe sized to a dimension approximately the same size as the treatmentsite, or even somewhat larger. This sizing further minimizes the risk ofthe implant moving in or slipping out of the treatment site.

Prior implant devices, such as the HES device, currently provide theuser with about 5 minutes of repositioning time. However, the implant 11of the present invention increases the length of repositioning time. Insome embodiments, the repositioning time during a procedure can beincreased to about 30 minutes. In this respect, the user is providedwith a longer repositioning time to better achieve a desired implantconfiguration

FIG. 2 shows an implant 11 similar to that shown in FIG. 1 after theexpansile element 1 has expanded through the gap 7 to a dimension largerthan the carrier member 2.

FIG. 3 shows an implant 11 wherein multiple expansile elements 1 runsomewhat parallel to each other through the carrier member 2. In oneembodiment, this configuration is constructed by looping a singleexpansile element 1 around the tip 4 of the implant 11 and tying bothends of the expansile element 1 to the proximal end of the carriermember 2. In another embodiment, multiple strands of the expansileelement 1 may be bonded along the length of the carrier member 2. Theconstruction of these embodiments may also comprise stretching theexpansile element 1 as previously described and/or forming gaps in thecarrier member 2.

FIG. 4 shows an embodiment wherein the implant 11 comprises a non-coilcarrier member 2. In one embodiment, the carrier member 2 is formed bycutting a tube or sheet of plastic such as polyimide, nylon, polyester,polyglycolic acid, polylactic acid, PEEK, Teflon, carbon fiber orpyrolytic carbon, silicone, or other polymers known in the art with, forexample; a cutting blade, laser, or water jet in order to form slots,holes, or other fenestrations through which the expansile element 1 maybe in contact with bodily fluids. The plastic in this embodiment mayalso comprise a radiopaque agent such as tungsten powder, iodine, orbarium sulfate. In another embodiment, the carrier member 2 is formed bycutting a tube or sheet of metal such as platinum, steel, tungsten,Nitinol, tantalum, titanium, chromium-cobalt alloy, or the like with,for example; acid etching, laser, water jet, or other techniques knownin the art. In another embodiment, the carrier member 2 is formed bybraiding, knitting, or wrapping metallic or plastic fibers in order toform fenestrations.

FIG. 5 shows an implant 11 comprising a carrier member 2, an expansileelement 1, and a stretch resistant member 10. The stretch resistantmember 10 is used to prevent the carrier member 2 from stretching orunwinding during delivery and repositioning. The stretch resistantmember 10 may be made from a variety of metallic or plastic fibers suchas steel, Nitinol, PET, PEEK, Nylon, Teflon, polyethylene, polyolefin,polyolefin elastomer, polypropylene, polylactic acid, polyglycolic acid,and various other suture materials known in the art. Construction of theimplant 11 may be by attaching the ends of the stretch resistant member10 to the ends of the carrier member 2 as described by U.S. Pat. No.6,013,084 to Ken and U.S. Pat. No. 5,217,484 to Marks both herebyincorporated by reference. Alternatively, the distal end of the stretchresistant member 10 may be attached near the distal end of the carriermember 2 and the proximal end to the stretch resistant member 10attached to the delivery system as described in co-pending applicationSer. No. 11/212,830 to Fitz.

FIG. 6 is an alternative embodiment comprising a stretch resistantmember 10 wrapped around, tied to, or intertwined with the expansileelement 1. This may occur over the length of the expansile element 1, orthe wrapping or tying may be in only one area to facilitate bonding theexpansile element 1 to the carrier element 2 by using the stretchresistant member 10 as a bonding element.

FIG. 7 shows a loop or fold 12 of the expansile element 1 protrudingoutside the carrier element 2. In some embodiments, it may be desirableto avoid this condition by, for example, stretching the expansileelement 1 as previously described. This would be done, for example, inembodiments configured for delivery through a small microcatheter toprevent the implant 11 from becoming stuck in the microcatheter duringdelivery. In other embodiments, slack may be added to the expansileelement 1 so that the loop or fold will be pre-formed into the implant11. This would be done in embodiments where, for example, a large amountof volumetric filling was necessary because the loops or folds wouldtend to increase the total length of the expansile element 1.

FIG. 8 shows an embodiment wherein the expansile element 1 is configuredto expand to a dimension larger than its initial dimension, but smallerthan the outer dimension of the carrier member 2. This may be done byadjusting the ratio of, for example, PEG di-acrylamide to sodiumacrylate in embodiments wherein the expansile element 1 comprises ahydrogel. Alternatively, a relatively high dose of radiation could beused to cross-link the expansile element 1, thus limiting its expansion.Embodiments such as shown in FIG. 8 are desirable when filling isnecessary and it is desirable to have a substrate for tissue growth andproliferation that the expansile element 1 provides. In an embodimentused to treat cerebral aneurysms, this configuration could be used as a“filling” coil. In one embodiment, the expansile element 1 comprises ahydrogel incorporating a porosigen as previously described to provide areticulated matrix to encourage cell growth and healing. Incorporating,for example, growth hormones or proteins in the expansile element 1 aspreviously described may further enhance the ability of the implant 11to elicit a biological response.

FIGS. 9-11 illustrate another preferred embodiment of an implant 11according to the present invention. This implant is generally similar tothe previously described embodiments, including an expansile element 1that is disposed within a carrier member 2. Additionally, a stretchresistant member 10 is positioned along a longitudinal axis of theexpansile element 1 and attached to the distal end of the carrier member2. The stretch resistant member 10 is preferably located within orpartially surrounded by the expansile element 1. Preferably, the stretchresistant member 10 is wrapped around a proximal portion of the carriermember 2 and attached near a heater coil 22 within a distal end of adelivery device 20, shown in FIG. 11.

As best seen in FIG. 9, the proximal end of the carrier member 2 caninclude a coiled region having a smaller diameter than the other coiledregions of the member 2. This smaller diameter coiled region allows thestretch resistant member 10 to be wrapped around the member 2 withoutextending outwards past the diameter of the other coiled regions of themember 2. Additionally, a covering material 5 can be further positionedover the smaller diameter coiled region without the loops of the stretchresistant member 10 being exposed. Preferably, this covering material 5is a laser, solder, adhesive, or melted hydrogel material.

As seen best in FIG. 9, the spacing of the helical coils of the carriermember can vary along the length of the implant 11. For example, thecoils can be located close to each other or touching each other near theproximal and distal ends while the center portion of the implant 11 canhave coils with larger spaces between them. In other words, the gapsbetween the coils can be larger along most of the implant 11 and smallernear the ends of the implant 11.

In one embodiment, this implant 11 is created according to the followingmethod. The expansile element 1 is created with hydrogel according tothe previously described techniques in this specification. In oneembodiment, the expansile element 1 is formed in a polymerization tubebetween about 0.025″ and 0.032″ ID. After polymerization, thepolymerization tube is cut into segments that are dried under vacuum.Once all water has been removed from the hydrogel, the dried hydrogel ispushed out of the polymerization tube using a mandrel. The hydrogel isthen washed in water three times, swelling the hydrogel and removingsodium chloride and unreacted monomers.

This expanded hydrogel is then skewered along its longitudinal axis(i.e., along an axis of its length) using a microcoil (or similarelongated tool). This skewing creates a pathway along the approximatecenter of the hydrogel filament so that a stretch resistant member 10can be later threaded through. Next, the skewered hydrogel is acidtreated by immersion into a hydrochloric acid solution, protonating thecarboxylic acid moieties of the sodium acrylate component of the polymernetwork. The skewered hydrogel is finally washed in alcohol to removeresidual acid and dried under a vacuum.

A gapped platinum coil is used for member 2, having an outer diameterranging from about 0.012″ to about 0.018″, filar ranging from about0.0015″ to about 0.0030″, and gaps 7 ranging from about 0.0015″ to about0.0075″. In another embodiment the gaps 7 range from about 0.00225″ toabout 0.00750″. In one embodiment, this platinum coil has an outerdiameter of about 0.012″, a filar of about 0.002″, and a gap 7 of about0.004″. In another embodiment, this platinum coil has an outer diameterof about 0.0125″, a filar of about 0.00225″, and a gap 7 of about0.0045″. This gapped platinum coil is wound over a mandrel and heat-setinto a secondary helical shape. The platinum coil is cut to a desiredimplant length and bonded to a coupling marker band or coupler 13 viasoldering, welding or adhesive (e.g., weld 15 in FIG. 9).

The coil used to skewer the hydrogel filament is removed, and an about0.0022″ polyolefin stretch-resistant thread for the stretch resistantmember 10 is threaded through the filament along the pathway left by thecoil. The hydrogel filament, which now has an outer diameter of betweenabout 0.010″ to about 0.018″ is stretched to an outer diameter betweenabout 0.006″ to about 0.012″ and inserted into the gapped platinum bodycoil. While still under tension, the hydrogel filament is bonded to thebody coil at both ends.

The stretch-resistant thread is knotted at the distal end of theplatinum coil and wrapped around the open coil gaps at the proximal end(i.e., the end with coupler 13). Both ends of the implant 11 are coveredwith adhesive 4 and 5 to secure the stretch resistant member 10 andencapsulate the ends of the expansile element 1. Finally, the implant 11is attached to a detachment pusher using the stretch resistant member 10that protrudes from the proximal end of the implant 11.

During use of the implant 11 of this embodiment, the implant 11 isadvanced via a detachment pusher 20 through a microcatheter (not shown).When the distal end of the microcatheter has reached a desired targetarea, the pusher 20 is advanced, thereby pushing the implant 11 out ofthe microcatheter. When the user wishes to detach the implant 11, aheater coil 22 is activated to break the stretch resistant member 10.Upon contact with the blood, the pH sensitive expansile element willexpand to a final diameter between about 0.020″ and 0.035″, allowing theuser about 5-10 minutes of working time.

In another embodiment of the invention, the implant 11 of FIG. 9includes a stretch-resistant member 10 composed of polyolefin and havingan outer diameter of about 0.0022″. The expansile element 1 is composedof a hydrogel of about 48% PEG 8000 diacrylamide and 52% sodiumacrylate. The member 2 is a gapped platinum coil having an outerdiameter between about 0.012″ and 0.020″ and more preferably about0.012″. The member 2 has a filar between about 0.0015″ and 0.005″ andmore preferably about 0.002″. The gap between winds of the member 2 ispreferably about 0.003″.

FIG. 12 illustrates a preferred embodiment of an implant 11 similar tothe previously described embodiment in which the gaps between winds ofthe member 2 are preferably between about 0.002″ and 0.020″.Additionally, the implant 11 contain one or more outer member 30 locatedat a proximal end of the implant 11, at a distal end of the implant,adjacent to the proximal or distal end of the implant, or at anycombination of these locations. In the example of FIG. 12, an outermember 30 is positioned at the proximal and distal ends of the implant11.

In one example, the outer member 30 is preferably composed of platinumcoil having a length between about 0.010″ and 0.120″ and more preferablybetween about 0.040″ and 0.080″. The internal diameter of the outermember 30 is preferably between about 0.012″ and 0.017″ and morepreferably between about 0.012″ and 0.0125″. The wire of the outermember 30 preferably has a filar between about 0.0015″ and about 0.003″and more preferably about 0.0015″.

In another example, the outer member 30 is composed of a slotted tubehaving a length between about 0.010″ and 0.120 and more preferablybetween about 0.040″ and 0.080″. The internal diameter of the slottedtube is preferably between about 0.012″ and 0.017″ and more preferablybetween about 0.012″ and 0.0125″. The thickness of the slotted tube ispreferably between about 0.001″ and 0.003″ and more preferably about0.0015″.

FIG. 13 illustrates another preferred embodiment of the implant 11 thatis generally similar to the previously described embodiment. However,this implant 11 further comprises a closed-wound platinum coil 32disposed over the stretch-resistant member 10. Preferably, thestretch-resistant member 10 is composed of polyethylene and has an outerdiameter of about 0.0009″. The closed-wound platinum coil 32 preferablyhas an outer diameter of about 0.006″ and has a wire filar of about0.0015″. The expansile element 1 is preferably composed of 48% PEG 8000diacrylamide and 52% sodium acrylate. The member 2 is a gapped platinumcoil having an outer diameter between about 0.012″ and 0.020″ and morepreferably between about 0.014″ and 0.015″. The member 2 has a filarbetween about 0.0015″ and 0.005″ and more preferably about 0.002″. Thegap between winds of the member 2 is preferably between about 0.002″ and0.020″ and more preferably 0.004″.

Preferably, the implant 11 of FIG. 13 is created by preparing expansileelement 1 with hydrogel as previously described in this specification.Prior to the acid treatment, the hydrated hydrogel is skewered with aplatinum coil 32. Preferably, the platinum coil 32 is heat-set into apredetermined helical shape with a defined pitch and diameter prior toskewering. A stiff and preferably platinum-based mandrel is insertedinto the platinum coil 32 to provide support during further treatmentsand construction of the implant 11.

Following the acid treatment of the hydrogel, the mandrel is removedfrom within the platinum coil 32 and replaced by stretch-resistantmember 10 (e.g., a polyolefin monofilament). Optionally, both themandrel and the platinum coil 32 can also be removed and replaced by thestretch-resistant member 10. The member 2 (e.g., a gapped platinum coil)is placed over the resulting subassembly and is sized appropriately toallow little or no free space within the internal diameter of the member2. The member 2 can optionally be wound and heat-set into a preliminaryand preferably helical shape of a defined pitch and diameter prior toplacing over the hydrogel and platinum coil 32.

Once the member 2 has been placed, it is bonded to the hydrogel usingadhesives at proximal and distal ends (preferably UV-cured adhesives).At this point, outer members 30 can optionally be located and bonded atone or more ends of the implant 11. The stretch-resistant member 10 isthen secured at both ends of the implant 11 and the implant 11 iscoupled to an electrical detachment mechanism as described elsewhere inthis specification.

In one embodiment of the invention a vaso-occlusive device comprises anexpansile polymer element having an outer surface, a carrier member thatcovers at least a portion of the outer surface of the expansile polymerelement, and wherein no carrier is disposed within the outer surface ofthe expansile element.

In another embodiment, a vaso-occlusive device comprises a coil having alumen and a hydrogel polymer having an outer surface wherein thehydrogel polymer is disposed within the lumen of the coil and whereinthe hydrogel polymer does not contain a coil within the outer surface ofthe hydrogel polymer.

In another embodiment, a vaso-occlusive device comprises a carriermember formed into a secondary configuration and an expansile element,wherein the expansile element is made from a polymer formulated to havesufficient softness that the expansile element will substantially takethe shape of the secondary configuration formed into the carrier memberwithout pre-treatment.

In another embodiment, a vaso-occlusive device comprises a carriermember formed into a secondary configuration and a substantiallycontinuous length of hydrogel, wherein the device will substantiallytake the shape of the secondary configuration formed into the carriermember without pre-treatment.

In another embodiment, a vaso-occlusive device comprises a microcoilhaving an inner lumen and an expansile element disposed within the innerlumen. In this embodiment the expansile element comprises a hydrogelselected from the group consisting of acrylamide, poly(ethylene glycol),Pluronic, and poly(propylene oxide).

In another embodiment, a vaso-occlusive device comprises a coil and ahydrogel polymer disposed at least partially within the coil wherein thehydrogel has an initial length and wherein the hydrogel polymer has beenstretched to a second length that is longer than the initial length.

In another embodiment, a vaso-occlusive device comprises an expansileelement and a carrier member defining an inner lumen, wherein theexpansile element is disposed within the inner lumen of the carriermember and wherein the expansile element has been stretched to a lengthsufficient to prevent a loop of the expansile element from protrudingthrough the carrier member.

The invention disclosed herein also includes a method of manufacturing amedical device. The method comprises providing a carrier member havingan inner lumen and an expansile element, inserting the expansile elementinto the inner lumen of the carrier member, and stretching the expansileelement.

In another embodiment, a vaso-occlusive device comprises an expansileelement encapsulated by a carrier element, wherein said expansileelement is comprised substantially entirely and substantially uniformlyof material having an expansile property.

In another embodiment, a vaso-occlusive device comprises a carrierelement and an expansile element wherein the carrier element has asecondary shape that is different from its primary shape and wherein theexpansile element is sufficiently flexible in a normal untreated stateto conform with the secondary shape of the carrier.

In another embodiment, a vaso-occlusive device includes a carrier and anexpansile element wherein the expansile element is fixed to the carrierin a manner such that the expansile element is in a stretched statealong the carrier.

In another embodiment, a vaso-occlusive device includes a carrier havinga plurality of gaps along the carrier and an expansile elementpositioned along an inside envelope of the carrier and wherein theexpansion of the expansile element is controlled such that the expansileelement expands into the gaps but not beyond the external envelope ofthe carrier.

In another embodiment, a vaso-occlusive device includes a carrier memberand an expansile element wherein the expansile element is comprised ofmultiple strands extending along the carrier.

In another embodiment, a vaso-occlusive device includes a carrier and anexpansile member wherein the carrier is a non-coiled cylindricallyshaped structure and wherein said expansile member is disposed insidesaid carrier.

In another embodiment, a vaso-occlusive device includes a carrier and anexpansile member and a stretch resistant member; said expansile memberand said stretch resistant member being disposed in an internal regionof the carrier and wherein the stretch resistant member is in tension onsaid carrier.

The invention disclosed herein also includes a method of treating alesion within a body. The method comprises providing a vaso-occlusivedevice comprising a carrier member and an expansile element wherein thecarrier member is formed into a secondary configuration that isapproximately the same diameter as the lesion and inserting thevaso-occlusive device into the lesion.

Although preferred embodiments of the invention have been described inthis specification and the accompanying drawings, it will be appreciatedthat a number of variations and modifications may suggest themselves tothose skilled in the pertinent arts. Thus, the scope of the presentinvention is not limited to the specific embodiments and examplesdescribed herein, but should be deemed to encompass alternativeembodiments and equivalents.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques. Notwithstanding that the numerical ranges and parameterssetting forth the broad scope of the invention are approximations, thenumerical values set forth in the specific examples are reported asprecisely as possible. Any numerical value, however, inherently containscertain errors necessarily resulting from the standard deviation foundin their respective testing measurements.

The terms “a,” “an,” “the” and similar referents used in the context ofdescribing the invention (especially in the context of the followingclaims) are to be construed to cover both the singular and the plural,unless otherwise indicated herein or clearly contradicted by context.Recitation of ranges of values herein is merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range. Unless otherwise indicated herein, eachindividual value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention otherwise claimed. No languagein the specification should be construed as indicating any non-claimedelement essential to the practice of the invention.

Groupings of alternative elements or embodiments of the inventiondisclosed herein are not to be construed as limitations. Each groupmember may be referred to and claimed individually or in any combinationwith other members of the group or other elements found herein. It isanticipated that one or more members of a group may be included in, ordeleted from, a group for reasons of convenience and/or patentability.When any such inclusion or deletion occurs, the specification is deemedto contain the group as modified thus fulfilling the written descriptionof all Markush groups used in the appended claims.

Certain embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Ofcourse, variations on these described embodiments will become apparentto those of ordinary skill in the art upon reading the foregoingdescription. The inventor expects skilled artisans to employ suchvariations as appropriate, and the inventors intend for the invention tobe practiced otherwise than specifically described herein. Accordingly,this invention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

Furthermore, numerous references have been made to patents and printedpublications throughout this specification. Each of the above-citedreferences and printed publications are individually incorporated hereinby reference in their entirety.

In closing, it is to be understood that the embodiments of the inventiondisclosed herein are illustrative of the principles of the presentinvention. Other modifications that may be employed are within the scopeof the invention. Thus, by way of example, but not of limitation,alternative configurations of the present invention may be utilized inaccordance with the teachings herein. Accordingly, the present inventionis not limited to that precisely as shown and described.

1. A device for implantation in an animal comprising: a helical carriermember; and a hydrogel having ionizable functional groups wherein saidhydrogel comprises a macromer of about 48% poly(ethylene glycol)di-acrylamide and a pH sensitive component of about 52% sodium.
 2. Adevice according to claim 1 wherein said macromer is cross-linked withat least one ethylenically unsaturated compound.
 3. A device accordingto claim 1 wherein said macromer is cross-linked with N,N′-methylenebisacrylamide, derivatives thereof, or combinations thereof.4. A device according to claim 1 wherein said hydrogel includes porescreated by a porosigen.
 5. A device according to claim 4 wherein saidporosigen is about 0.4 g/g sodium chloride.
 6. A device according toclaim 5 wherein said sodium chloride has a particle size of about 10microns.
 7. A device according to claim 1 wherein said helical coilincludes gaps ranging from about 0.0015″ to about 0.00750″.
 8. A deviceaccording to claim 7 wherein said gap comprises 0.003″.
 9. A deviceaccording to claim 1 further comprising a stretch resistant memberdisposed within said hydrogel member and wrapped around at least aportion of said helical carrier member.
 10. The implant device of claim1, wherein said helical carrier member comprises a coiled region havinga first diameter and a coiled region having a second diameter.
 11. Theimplant device of claim 1 wherein said hydrogel expands from a diameterof about is about 0.006″-0.007″ to a diameter of about 0.02″ afterexpansion.
 12. A device for implantation in an animal comprising: ahelical carrier member having gaps ranging from about 0.0015″ to about0.00750″; and a hydrogel.
 13. A device according to claim 12 comprisinga hydrogel having ionizable functional groups wherein said hydrogelcomprises at least a macromer of about 48% poly(ethylene glycol)di-acrylamide and a pH sensitive component of about 52% sodium.
 14. Theimplant device of claim 12, wherein said hydrogel includes pores createdby a porosigen.
 15. The implant device of claim 14, wherein saidporosigen is about 0.4 g/g sodium chloride.
 16. The implant device ofclaim 15, wherein said sodium chloride has a particle size of about 10microns.
 17. A device according to claim 12 wherein said gap comprises0.003″.
 18. A device according to claim 12 further comprising a stretchresistant member disposed within said hydrogel member and wrapped aroundat least a portion of said helical carrier member.
 19. The implantdevice of claim 12, wherein said helical carrier member comprises acoiled region having a first diameter and a coiled region having asecond diameter.
 20. The implant device of claim 12 wherein saidhydrogel expands from a diameter of about is about 0.006″-0.007″ to adiameter of about 0.02″ after expansion.
 21. An implant devicecomprising: a helical carrier member having a gap comprising 0.003″; ahydrogel member disposed within said helical carrier member; and, astretch resistant member disposed within said hydrogel member andwrapped around at least a portion of said carrier member; wherein saidhydrogel comprises a macromer of about 48% poly(ethylene glycol)di-acrylamide and a pH sensitive component of about 52% sodium acrylate.22. The implant device of claim 21 wherein said hydrogel expands from adiameter of about is about 0.006″-0.007″ to a diameter of about 0.02″after expansion.